The company has been on the list for several years, reaching the number two position last year. This is the first time, however, it has achieved the number one spot.

"We are very proud and deeply honoured that IAOP has recognised ISS as the world's best outsourcing company," said Jeff Gravenhorst, ISS Group ceo.

He continued: "We take the ranking as a vote of confidence in ISS and our global platform from which we integrate and self-deliver a complete set of facility services such as catering, cleaning, security, property and support services across the globe."

"As applicants continually raise the bar and as the outsourcing industry continues to grow and mature in many markets, competition is tougher," said Jag Dalal, managing director of thought leadership, IAOP and chairman of the judges' panel.

"Being named on The Global Outsourcing 100 is a great achievement, particularly given the strong competition, and we are proud to recognise ISS for their excellence."

"As 2013 begins to see moderate growth in the economy, choosing the right outsourcing partners will be more important than ever," said IAOP chairman Michael Corbett. "The Global Outsourcing 100 and the World's Best Outsourcing Advisors lists help companies easily identify partners that will help them emerge as leaders."